Torrefaction is generally known as the process of thermal treatment of various cellulosic materials under an inert (i.e., non-oxidizing) atmosphere to convert such materials into a more useful product. For example, wood when dried and heated to a temperature of about 200° C. to 290° C. becomes what has been referred to as “torrefied wood”, i.e., a carbon-neutral product with a high fixed carbon content, a high caloric value, a very low moisture content, and which is generally non-hygroscopic and rot proof, having retained practically all the pyroligneous compounds. Examples of torrefaction and equipment therefore are disclosed in U.S. Pat. No. 4,787,917 and U.S. Patent Application Pub. No. 2003/0221363, the disclosures of which are incorporated herein by reference.
The present invention relates in general to improvements in systems and methods for drying and torrefaction of various materials.